The vast majority of Superfund sites in the U.S and the Baltimore/Chesapeake Bay area contain mixtures of[unreadable] organic and inorganic compounds that contaminate underlying aquifers. The environmental fate of these[unreadable] contaminants, and ultimately human exposure to them, is governed primarily by their interactions with[unreadable] microorganisms, which?individually or as a community?drive the process of in situ bioremediation.[unreadable] Whereas single pollutant/microorganism interactions can be determined easily in the lab, no satisfactory[unreadable] tools exist for predicting the fate of mixtures in the environment. Our long-term goal is to improve the[unreadable] success rate of bioremediation at sites containing complex chemical mixtures by using in situ microcosm[unreadable] array (ISMA) technology. The ISMA is a field-deployable, miniaturized laboratory consisting of a large[unreadable] number of small microcosms arranged in parallel. Upon deployment, incubation, and retrieval from a[unreadable] groundwater well, the ISMA can be analyzed to reveal the impact of mixture components on the rates of[unreadable] Dollutant degradation and on the structure and function of microbial communities. We hypothesize that the[unreadable] ISMA can aid in the design of bioremediation strategies because: (1) individual ISMA microcosms can be[unreadable] amended with multiple test substances to elucidate the effect of mixture components on microorganisms; (2)[unreadable] the response of microorganisms to presented compounds manifests itself as changes in biomass,[unreadable] community structure and function; and (3) these changes can be detected conveniently by biochemical,[unreadable] genetic and proteomic strategies. Based on the above observations, the specific aims of the project are to:[unreadable] 1. Determine the reproducibility and discriminatory power of the ISMA technology. We will explore how[unreadable] varying concentrations of inducers and co-contaminants in synthetic groundwater modulate the expression of[unreadable] the dioxin dioxygenase (DDase) of Sphingomonas wittichii Strain RW1, by using a large number of replicates[unreadable] in conjunction with semi-automated, high-throughput proteomic mass spectrometry.[unreadable] 2. Demonstrate in controlled laboratory conditions how the ISMA can reveal additive, synergistic, and[unreadable] antagonistic effects of mixture components on microbial communities. We will use defined mixtures of[unreadable] chemicals (e.g., dioxins, PCBs, PAHs, tolualdeyhyde, Cd, Cr, Co, Pb, Hg, Zn, Ni) and bacteria (five[unreadable] bioremediation agents) to study these effects in various permutations.[unreadable] 3. Evaluate the utility of the ISMA technology in simulated field conditions. We will conduct ISMA laboratory[unreadable] experiments using nonsterile groundwater, sediment, and natural microbial communities.[unreadable] 4. Deploy the ISMA device at a Maryland Superfund site. We will assess the utility of the new technology in a[unreadable] field demonstration study by examining survival of and DDase expression by Strain RW1 in situ, and by[unreadable] elucidating the impact of this introduced bacterium on the indigenous microbial community at the site.